The present invention relates to an improved generator. More specifically, the present invention provides an improved generator having an improved rotor assembly including an air deflector.
Without a generator, the electrical load of a vehicle would quickly drain a fully charged battery. In a vehicle, a generator producing alternating current (AC), known as an alternator, is often mounted at the front of the engine and is linked to the engine crankshaft pulley by a drive belt. When the engine turns the drive belt, the drive belt turns a shaft in the alternator, and current is generated. Current is produced in an alternator when a wire intercepts a magnetic field. In an alternator, it is the wire, in coiled form, that is held stationary and the magnetic field is turned so that the magnetic field passes through the wire. Thus, alternators include a stationary part, the stator, and a rotating part, the rotor.
The stator may include stationary coils or slotted pins or members that surround a rotor. As the rotor is turned by the car engine, the alternating magnetic field created by the rotor is intercepted by the stationary coils, pins or members, and current flows through the stator first in one direction, then in the other, resulting in alternating current. As the rotor is turned, air flow within the assembly will produce noise in the audible range that will emanate from the alternator assembly.
The rotor includes an electromagnet that is magnetized by current from the battery. The electromagnet may include slip rings, rotor windings, and north and south pole members surrounding the rotor windings. Current from the battery flows through the slip rings to the rotor windings. North and south pole members have pole claws shaped like interlocking teeth surrounding the rotor windings. The north and south pole members create an alternating magnetic field as the rotor turns.
A housing surrounds the rotor and stator assembly. The stator is fixed relative to the housing and the rotor shaft is rotatably mounted relative to the housing. Because the battery and electrical components in the car work on direct current (DC), the AC output of the alternator must be converted to DC. This is done with rectifiers which pass current in one direction only. Because, the components within the alternator produce heat and because the alternator operates under high under hood temperatures, a fan is included in the alternator assembly. The fan may be placed inside or outside of the housing to increase airflow between the rotor and stator and to increase airflow through openings in the housing. The fan blades may face inward toward the central portion of the alternator or outward away from the central portion of the alternator. Rotation of the fan increases airflow within the alternator and helps to reduce heat.
U.S. Pat. No. 4,617,485, assigned to Nippondenso Co., Ltd., describes one attempt to reduce windage noise produced as a result of airflow interference between the rotor and the stator utilizing spacers centrally mounted between adjacent pole core claws. The spacers are comprised of either discrete wedges mounted with an interference fit or are integrally formed into a ring. As described, the spacers are mounted centrally between opposing pole core claws. It appears that the spacers of this invention must be mounted relative to the claws either individually as separate wedges or as a ring. It appears that the direct fit between the spacers and claws will vary with manufacturing tolerances and temperature.
The inventors of the present invention have recognized a need for an improved method of reducing noise emanating from the generator. Unlike known methods, Applicants have invented a deflector that does not require separate installation of individual wedges or a free floating ring. Further, the fit of the present invention will be more independent from temperature variations. The present invention also directs airflow in a manner different from known methods. Additional advantages of the present invention are described and will become apparent with reference to the drawings and specification provided herein.
An exemplary embodiment of the present invention includes a rotor and a deflector for use in an improved generator. The rotor includes a rotor shaft extending in an axial direction and defining an axis of rotation, a first pole member mounted on a first end of the shaft and having a first set of teeth, and a second pole member mounted on a second end of the shaft and having a second set of teeth. The first and second pole members are opposing one another and comprise north and south pole members. The first set of pole claws and second set of pole claws are intermeshed and spaced apart from one another. The deflector is supported about either of the first end or second end of the shaft and corresponds to the adjacent pole member mounted on the same end of the shaft. The deflector is adapted to rotate with the corresponding pole member and includes a plurality of non-magnetic axial extensions having a base portion extending between adjacent pole claws of the corresponding member and terminating proximal an intermeshed pole claw of the opposing pole member. The axial extensions provide a more uniform circumference creating more desirable airflow as the rotor rotates about its axis. The resulting airflow results in less noise as less air impinges against a surrounding stator. The deflector axial extensions may further include a first side extension and a second side extension each further extending from the base portion and surrounding the intermeshed pole claw of the opposing pole member. The deflector disc may further include at least one aperture for improving axial airflow within the pole members.
Additional aspects of the present invention will become apparent with reference to the following Figures, detailed description and claims.